The present invention pertains to enclosures and housings for electrochemical cells and cell assemblies. More particularly it pertains to enclosures and housings for one or more small primary and secondary cells of the types which are often used in the form of a battery of one or more interconnected cells. Individual primary and secondary cells are manufactured in a limited number of standard configurations, each with generally fixed capabilities in available voltage, current and duration of output. However, the wide range of devices using these cells today have power demands that frequently exceed the capabilities of individual cells. Both primary and secondary electrochemical cells are combined in various ways to satisfy these demands. In one approach, the cells are introduced individually, loosely, to the powered device to be combined by the device's own internal circuit elements. Alternatively, the cells are bundled together to form an integrated battery pack.
Circuit elements can be incorporated with one or more cells to form an integrated battery pack. These circuit elements perform a number of functions, including the interconnection of the cells for battery packs having more than one cell, and the production of performance characteristics meeting the specified demand. These packs may be produced independent of the powered device and then inserted on demand as a unit. This type of integrated battery pack has become particularly favored as devices such as cellular phones and portable computers have increased demands on their batteries. The integrated battery pack also has increased convenience in the reduction of the number of parts handled by the user. As well, in the case of secondary cells, the packaged cell or cells may be more conveniently connected as a unit to a recharging device.
The introduction of high performance cell chemistries such as lithium ion based cells have added new demands on packaged cell assemblies. Lithium ion cells are preferably not used connected directly to the associated powered device. Rather, they are used in combination with protective circuit elements which protect against over-voltage or under-voltage on discharge or in cases of external shorting. Also "smart" battery circuit elements may be incorporated to provide control of the charge and discharge of the cell. These circuit elements are often themselves packaged on a circuit board which is assembled with one or more cells to form a battery assembly. The "smart" circuit elements can also monitor, for example, battery temperature and voltage for the purpose of enhancing operational life of the battery and avoiding cell failures resulting from unacceptable battery conditions. Therefore, their incorporation into the lithium ion battery pack is desirable. Rough handling, vibration or impact events can compromise the continued operation of these "smart" battery circuit elements and lead to unacceptable battery conditions. An external housing or enclosure which retains the individual cells as an assembly can also provide protection to protective and "smart" circuit elements. Enclosures such as shrink-wrapped plastic sleeves are often used to physically bundle cells together. But the nature of shrink-wrap materials does not lend them to protection of fragile elements such as circuit boards. Assemblies using shrink-wrap and similar coverings also generally cannot meet many industry standards such as those for flammability, and shock and vibration environments. Completely enclosing, rigid, plastic housings are often used to construct integrated battery packs for devices such as lap-top computers and cellular phones. Although these customized structures can provide a high level of protection and function, they generally incur high production costs. This is due to their relatively complex shapes requiring the use of production processes such as injection molding having significant initial tooling expenses. As well as being costly, these processes generally have a long lead time to produce a finished product. This is not conducive to consumer battery production which must respond quickly to changing product demand. Particularly in the circumstance of demands for small lot production, customized high initial cost enclosure structures are often not feasible.
What is needed is a method of easily and cheaply producing protective enclosures for cell assemblies incorporating circuit elements. Such enclosures should be easily adaptable to a variety of cell configurations and sizes and should not require customized tooling.